Problem: $ { \left[\begin{array}{r}{3} \\ {2} \\ {3}\end{array}\right]+\left[\begin{array}{r}{1} \\ {3} \\ {1}\end{array}\right] = {?} } $
To find the sum of two matrices, add the corresponding items between each matrix. ${\left[\begin{array}{r}{3}+{1} \\ {2}+{3} \\ {3}+{1}\end{array}\right]}$ Now, simplify: ${\left[\begin{array}{r}{4} \\ {5} \\ {4}\end{array}\right]}$